do the tires appear small though? i just feel like something looks off about it, anyone else think so?

IF you truly got 215/40R18 - they will look small. Narrower section width and the 40 series is 40% of that 215. OEM for these wheels was 215/45R18, and so you would be running a much shorter sidewall than OEM, and shorter than the suggested 225/40R18.